Intrinsic interface exchange coupling of ferromagnetic nanodomains in a charge ordered manganite

Abstract

We present a detailed magnetic study of the Pr 1/3 Ca 2/3 MnO 3 manganite, where we observe the presence of small ferromagnetic ͑FM͒ domains ͑diameter ϳ10 Å͒ immersed within the charge-ordered antiferromagnetic ͑AFM͒ host. Due to the interaction of the FM nanodroplets with a disordered AFM shell, the low-temperature magnetization loops present exchange bias ͑EB͒ under cooling in an applied magnetic field. Our analysis of the cooling field dependence of the EB yields an antiferromagnetic interface exchange coupling comparable to the bulk exchange constant of the AFM phase. We also observe training effect of the EB, which is successfully described in terms of a preexisting relaxation model developed for other classical EB systems. This work provides the first evidence of intrinsic interface exchange coupling in phase separated manganites.

Phase coexistence and magnetic anisotropy in polycrystalline and nanocrystalline LaMnO3+δ

“…Noticeably, the M(H) loop for the bulk sample did not close when the field was swept back from negative to positive saturation at 2 T. A similar feature was reported on a polycrystalline Pr 1=3 Ca 2=3 MnO 3 and attributed to the coexistence of the FM and AFM phases. 12 Noticeably this feature was not pronounced in the nano sample, which could be associated with the strong suppression of the AFM peak in the ND spectra for this sample. Overall, our magnetic and neutron diffraction data consistently indicated the coexistence of the FM and AFM phases in the bulk and nano samples, and size reduction to the nanometer scale ($15 nm) significantly suppressed the AFM phase while inducing surface spin disorder in the material.…”

Dynamic enhancement of the exchange bias training effect

“…30 and 31 and evidenced for diverse exchange coupled systems. 27,28,30,31,34 Note that Eq. ͑6͒ involves three fitting parameters.…”

“…EB and the accompanying training effect have been observed in various magnetic systems ranging from core shell magnetic granules 25 and AF/FM thin film heterolayers 14,26 to intrinsic EB taking place at natural interfaces of ferromagnetic nanodomains embedded in an AF matrix of charge ordered manganites. 27 …”

Magnetic Properties of La0.8K0.2MnO3Nanoparticles

“…EB phenomena were observed in various materials like Laves phases, intermetallic compounds and alloys, binary alloys, Heusler alloys [2] or on layered bulk fluorometallo complex [3] where different aspects of magnetism were focused from the EB effect. The first evidence of the EB effect in mixed-valent manganites having perovskite structure was reported in a spontaneously phase separated system Pr 1/3 Ca 2/3 MnO 3 [4] which stimulated new interest for study of the EB effect in structurally single-phase compounds. The EB phenomena attributed to the spontaneous phase separation are very often observed in manganites with different perovskite structures.…”